The penetration of ions into the magnetosphere through the magnetopause turbulent current sheet

Abstract. This paper reports the results of numerical modeling of magnetosheath ion motion in the magnetopause current sheet (MCS) in the presence of magnetic fluctuations. Our model of magnetic field turbulence has a power law spectrum in the wave vector space, reaches maximum intensity in the center of MCS, and decreases towards the magnetosheath and magnetosphere boundaries. We calculated the density profile across the MCS. We also calculated the number of particles entering the magnetosphere, reflected from the magnetopause and escaping from the flanks, as a function of the fluctuation level of the turbulence and magnetic field shear parameter. All of these quantities appeared to be strongly dependent on the fluctuation level, but not on the magnetic field shear parameter. For the highest fluctuation levels the number of particles entering the magnetosphere does not exceed 15% of the total number of particles launched from the magnetosheath side of the MCS; the modeling also reproduced the effective reflection of the magnetosheath flow from very high levels of magnetic fluctuations.Key words. Magnetospheric physics (magnetosheath; magnetospheric configuration and dynamics; turbulence)

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Ion motion in the current sheet with sheared magnetic field – Part 1: Quasi-adiabatic theory

Nonlinear Processes in Geophysics ◽

10.5194/npg-20-163-2013 ◽

2013 ◽

Vol 20 (1) ◽

pp. 163-178 ◽

Cited By ~ 18

Author(s):

A. V. Artemyev ◽

A. I. Neishtadt ◽

L. M. Zelenyi

Keyword(s):

Magnetic Field ◽

Current Sheet ◽

Analytical Description ◽

Particle Energy ◽

Tangential Component ◽

Adiabatic Invariant ◽

Ion Motion ◽

Adiabatic Theory ◽

Fast Oscillations ◽

The Magnetic Field

Abstract. We present a theory of trapped ion motion in the magnetotail current sheet with a constant dawn–dusk component of the magnetic field. Particle trajectories are described analytically using the quasi-adiabatic invariant corresponding to averaging of fast oscillations around the tangential component of the magnetic field. We consider particle dynamics in the quasi-adiabatic approximation and demonstrate that the principal role is played by large (so called geometrical) jumps of the quasi-adiabatic invariant. These jumps appear due to the current sheet asymmetry related to the presence of the dawn–dusk magnetic field. The analytical description is compared with results of numerical integration. We show that there are four possible regimes of particle motion. Each regime is characterized by certain ranges of values of the dawn–dusk magnetic field and particle energy. We find the critical value of the dawn–dusk magnetic field, where jumps of the quasi-adiabatic invariant vanish.

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Ion motion in the current sheet with sheared magnetic field – Part 2: Non-adiabatic effects

Nonlinear Processes in Geophysics ◽

10.5194/npg-20-899-2013 ◽

2013 ◽

Vol 20 (5) ◽

pp. 899-919 ◽

Cited By ~ 7

Author(s):

A. V. Artemyev ◽

A. I. Neishtadt ◽

L. M. Zelenyi

Keyword(s):

Magnetic Field ◽

Current Sheet ◽

Particle Motion ◽

Phase Plane ◽

Time Interval ◽

Ion Motion ◽

Average Value ◽

Structure And Dynamics ◽

Adiabatic Theory ◽

The Magnetic Field

Abstract. We investigate dynamics of charged particles in current sheets with the sheared magnetic field. In our previouspaper (Artemyev et al., 2013) we studied the particle motion in such magnetic field configurations on the basis of the quasi-adiabatic theory and conservation of the quasi-adiabatic invariant. In this paper we concentrate on violation of the adiabaticity due to jumps of this invariant and the corresponding effects of stochastization of a particle motion. We compare effects of geometrical and dynamical jumps, which occur due to the presence of the separatrix in the phase plane of charged particle motion. We show that due to the presence of the magnetic field shear, the average value of dynamical jumps is not equal to zero. This effect results in the decrease of the time interval necessary for stochastization of trapped particle motion. We investigate also the effect of the magnetic field shear on transient trajectories, which cross the current sheet boundaries. Presence of the magnetic field shear leads to the asymmetry of reflection and transition of particles in the current sheet. We discuss the possible influence of single-particle effects revealed in this paper on the current sheet structure and dynamics.

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Magnetic turbulence and particle dynamics in the Earth’s magnetotail

Annales Geophysicae ◽

10.5194/angeo-21-1947-2003 ◽

2003 ◽

Vol 21 (9) ◽

pp. 1947-1953 ◽

Cited By ~ 9

Author(s):

G. Zimbardo ◽

A. Greco ◽

A. L. Taktakishvili ◽

P. Veltri ◽

L. M. Zelenyi

Keyword(s):

Magnetic Field ◽

Current Sheet ◽

Sheet Thickness ◽

Particle Dynamics ◽

Particle Simulation ◽

Mhd Waves ◽

Magnetic Fluctuations ◽

Magnetic Turbulence ◽

Magnetospheric Configuration And Dynamics ◽

Interplanetary Physics

Abstract. The influence of magnetic turbulence in the near-Earth magnetotail on ion motion is investigated by numerical simulation. The magnetotail current sheet is modelled as a magnetic field reversal with a normal magnetic field com-ponent Bn , plus a three-dimensional spectrum of magnetic fluctuations dB which represents the observed magnetic turbulence. The dawn-dusk electric field Ey is also considered. A test particle simulation is performed using different values of Bn and of the fluctuation level dB/B0. We show that when the magnetic fluctuations are taken into account, the particle dynamics is deeply affected, giving rise to an increase in the cross tail transport, ion heating, and current sheet thickness. For strong enough turbulence, the current splits in two layers, in agreement with recent Cluster observations.Key words. Magnetospheric physics (magnetospheric configuration and dynamics) – Interplanetary physics (MHD waves and turbulence) – Electromagnetics (numerical methods)

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Solar wind and substorm excitation of the wavy current sheet

Annales Geophysicae ◽

10.5194/angeo-27-2457-2009 ◽

2009 ◽

Vol 27 (6) ◽

pp. 2457-2474 ◽

Cited By ~ 25

Author(s):

C. Forsyth ◽

M. Lester ◽

R. C. Fear ◽

E. Lucek ◽

I. Dandouras ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Current Sheet ◽

Pressure Pulse ◽

Wind Pressure ◽

Expansion Velocity ◽

Solar Wind Pressure ◽

Wave Models ◽

Best Fit ◽

The Magnetic Field

Abstract. Following a solar wind pressure pulse on 3 August 2001, GOES 8, GOES 10, Cluster and Polar observed dipolarizations of the magnetic field, accompanied by an eastward expansion of the aurora observed by IMAGE, indicating the occurrence of two substorms. Prior to the first substorm, the motion of the plasma sheet with respect to Cluster was in the ZGSM direction. Observations following the substorms show the occurrence of current sheet waves moving predominantly in the −YGSM direction. Following the second substorm, the current sheet waves caused multiple current sheet crossings of the Cluster spacecraft, previously studied by Zhang et al. (2002). We further this study to show that the velocity of the current sheet waves was similar to the expansion velocity of the substorm aurora and the expansion of the dipolarization regions in the magnetotail. Furthermore, we compare these results with the current sheet wave models of Golovchanskaya and Maltsev (2005) and Erkaev et al. (2008). We find that the Erkaev et al. (2008) model gives the best fit to the observations.

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High magnetic field NMR investigation of the spin density wave phase of TMTSF2PF6

Journal de Physique IV (Proceedings) ◽

10.1051/jp4:20020445 ◽

2002 ◽

Vol 12 (9) ◽

pp. 389-389

Author(s):

W. G. Clark ◽

F. Zamborsky ◽

B. Alavi ◽

P. Vonlanthen ◽

W. Moulton ◽

...

Keyword(s):

Magnetic Field ◽

Spin Density ◽

Density Wave ◽

Spin Density Wave ◽

Proton Relaxation ◽

High Magnetic Fields ◽

Organic Conductor ◽

First Order ◽

The Magnetic Field ◽

Very High

We report proton NMR measurements of the effect of very high magnetic fields up to 44.7 T (1.9 GHz) on the spin density wave (SDW) transition of the organic conductor TMTSF2PF6. Up to 1.8 GHz, no effect of critical slowing close to the transition is seen on the proton relaxation rate (1/T1), which is determined by the SDW fluctuations associated with the phase transition at the NMR frequency. Thus, the correlation time for such fluctuations is less than $1O^{-10}$s. A possible explanation for the absence of longer correlation times is that the transition is weakly first order, so that the full critical divergence is never achieved. The measurements also show a dependence of the transition temperature on the orientation of the magnetic field and a quadratic dependence on its magnitude that agrees with earlier transport measurements at lower fields. The UCLA part of this work was supported by NSF Grant DMR-0072524.

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Analysis of the magnetic field discontinuity at the potential field source surface and Schatten Current Sheet interface in the Wang-Sheeley-Arge model

Journal of Geophysical Research Atmospheres ◽

10.1029/2007ja012330 ◽

2008 ◽

Vol 113 (A8) ◽

pp. n/a-n/a ◽

Cited By ~ 15

Author(s):

S. L. McGregor ◽

W. J. Hughes ◽

C. N. Arge ◽

M. J. Owens

Keyword(s):

Magnetic Field ◽

Current Sheet ◽

Potential Field ◽

Source Surface ◽

Field Source ◽

The Magnetic Field

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The Magnetic Field Turbulence at Comet Halley Observed by Vega 1 and 2

Cometary Plasma Processes - Geophysical Monograph Series ◽

10.1029/gm061p0273 ◽

2013 ◽

pp. 273-276

Author(s):

G. Le ◽

C. T. Russell ◽

K. Schwingenschuh ◽

W. Riedler

Keyword(s):

Magnetic Field ◽

Magnetic Field Turbulence ◽

Comet Halley ◽

The Magnetic Field ◽

Vega 1

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Ephemeral states in protein folding under force captured with a magnetic tweezers design

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1821284116 ◽

2019 ◽

Vol 116 (16) ◽

pp. 7873-7878 ◽

Cited By ~ 24

Author(s):

Rafael Tapia-Rojo ◽

Edward C. Eckels ◽

Julio M. Fernández

Keyword(s):

Magnetic Field ◽

Molten Globule ◽

Magnetic Tweezers ◽

Protein L ◽

High Frequencies ◽

Electric Signals ◽

Very High Frequencies ◽

The Magnetic Field ◽

Very High ◽

Unique Capability

Magnetic tape heads are ubiquitously used to read and record on magnetic tapes in technologies as diverse as old VHS tapes, modern hard-drive disks, or magnetic bands on credit cards. Their design highlights the ability to convert electric signals into fluctuations of the magnetic field at very high frequencies, which is essential for the high-density storage demanded nowadays. Here, we twist this conventional use of tape heads to implement one in a magnetic tweezers design, which offers the unique capability of changing the force with a bandwidth of ∼10 kHz. We calibrate our instrument by developing an analytical expression that predicts the magnetic force acting on a superparamagnetic bead based on the Karlqvist approximation of the magnetic field created by a tape head. This theory is validated by measuring the force dependence of protein L unfolding/folding step sizes and the folding properties of the R3 talin domain. We demonstrate the potential of our instrument by carrying out millisecond-long quenches to capture the formation of the ephemeral molten globule state in protein L, which has never been observed before. Our instrument provides the capability of interrogating individual molecules under fast-changing forces with a control and resolution below a fraction of a piconewton, opening a range of force spectroscopy protocols to study protein dynamics under force.

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Kinetic Alfvén solitons in a low-beta plasma

Journal of Plasma Physics ◽

10.1017/s0022377896004849 ◽

1997 ◽

Vol 57 (2) ◽

pp. 235-245 ◽

Cited By ~ 4

Author(s):

B. C. KALITA ◽

R. P. BHATTA

Keyword(s):

Magnetic Field ◽

Mach Number ◽

Solitary Waves ◽

Magnetic Pressure ◽

Hot Electrons ◽

Mass Ratio ◽

Ion Motion ◽

Electron Inertia ◽

Theoretical Investigations ◽

The Magnetic Field

Kinetic Alfvén solitons with hot electrons and finite electron inertia in a low-beta (β=8πn0T/B2G, the ratio of the kinetic to the magnetic pressure) plasma is studied analytically, with the ion motion being considered dominant through the polarization drift. Both compressive and rarefactive kinetic Alfvén solitons are found to exist within a definite range of kz (the direction of propagation of the kinetic Alfvén solitary waves with respect to the direction of the magnetic field) for each pair of assigned values of β and M (Mach number). Unlike in previous theoretical investigations, β appears as an explicit parameter for the kinetic Alfvén solitons in this case. In addition, consideration of the electron pressure gradient is found to suppress the speed of both the Alfvén solitons considerably for A (=2QM2/βk2z, with Q the electron-to-ion mass ratio) less than unity.

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